(cba:news) TT Ari in its darkest lair

Joe Patterson jop at astro.columbia.edu
Tue Nov 10 13:24:45 EST 2009

Dear CBAers,

Some amazing light curves of the quiescent TT Ari coming from the 
western USA observers, plus Mike Potter in Maryland who has managed to 
extend the coverage by 2-3 hours to the east.   I'm still hoping for 
good things from Europe, but I fear that weather there has turned bad - 
except for Enrique Agustino (Spain) who has been waging a heroic 
struggle with a 4-inch telescope (I think!).  Just a little, so far, 
from NZ and AU, but hope springs eternal there too.

I've never seen anything like these light curves.  In fact, no one has - 
not for TT Ari, and not for any other CV.  About 7 out of every 11 
hours, the star is down at V=16.3, and shows the ORBITAL period - for 
the first time ever.  There is then no activity, just a "heating" light 
curve which is likely the result of the hot WD illuminating the 
secondary's face.  Then the star goes into convulsions at V~15 for 4 
hours, then rests again... to repeat the cycle about every 11 hours. 
Just flat astounding.

So far, we've learned more from the V (or, if you can't spare the 
photons, clear) light curves than from the multicolor photometry.  But 
that's probably because it has been at true quiescence for only 1 week. 
  Fortuitously I'm about to leave on an observing run with the 2.4 m 
telescope; if weather permits, I'll spin filters and likely deconvolve 
this star into M dwarf and hot WD.  The flickering itself, when it's 
there, is broadband and not too likely to cough up much information from 
multiband observations.  I slightly recommend choosing one filter and 
sticking with it.  Also, there's value in preserving your setup as much 
as feasible; I've had enough simultaneous coverage to calibrate the 
various observers.

I say "slightly recommend" because this is in the absence of real 
knowledge about what we are observing.  A year from now, I'll have a 
more definite opinion about how we *should* have observed it!

More info about other stars tomorrow.  Is there help on the way from 
other longitudes re TT Ari?  It would be great - the coherence of this 
11 hour cycle is far from established, and it's a damn tough periodicity 
to evaluate!


More information about the cba-public mailing list